Question 1

What is ICD-10 code H21.303?

Accepted Answer

H21.303 is the ICD-10-CM diagnosis code for Idiopathic cysts of iris, ciliary body or anterior chamber, bilateral. Fluid-filled sacs in the iris or front part of the eye that develop without a known cause, affecting both eyes. H21.303 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. H21.303 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Question 2

Is H21.303 an HCC code?

Accepted Answer

No. H21.303 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is H21.303 billable?

Accepted Answer

Yes. H21.303 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. H21.303 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Question 4

What is the V28 vs V24 difference for H21.303?

Accepted Answer

H21.303 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards H21.303 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

Question 5

What should coders know when reporting H21.303?

Accepted Answer

Verify bilateral involvement is documented before assigning this code; if only one eye is affected, use the appropriate unilateral code instead. Idiopathic cysts are those without an identifiable underlying cause; ensure the cyst type is not specified as exudative or implantation.

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H21.303

Is H21.303 an HCC code?

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Open H21.303 in the Interactive Encoder

H21.303 ICD-10-CM Code: Idiopathic cysts of iris, ciliary body or anterior chamber, bilateral

HCC Buddy Code Card

H21.303

Is H21.303 an HCC code?

What This Code Means

Coding Tips

Child Codes

Code Hierarchy

Open H21.303 in the Interactive Encoder